1. Technical Field
The present invention relates to a tablet computer capable of being coupled to an external computer, and specifically to such tablet computer capable of switching its operation modes when coupled to an external computer.
2. Description of the Related Art
(1) Graphics Tablet (Digitizer) and Pen Display
A graphics tablet or a digitizer is widely used among users who wish to create hand-drawn images and graphics on a computer, similar to the way a person draws images with a pencil and paper. A typical graphics tablet includes a flat surface, upon which the user may “draw” or trace an image using a stylus or a pen-like drawing implement. The image generally does not appear on the tablet itself but, rather, is displayed on the monitor of an external computer, to which the graphics tablet is connected.
Some graphics tablets incorporate an LCD screen into the tablet itself such that the user's hand-drawn images appear on the tablet itself. These devices are called pen displays, one example of which is the Cintiq® line of pen displays available from WACOM®. A pen display allows the user to draw directly on the display surface. A pen display is required to be connected, via a wired or wireless connection, to an external computer having greater computational resources, such as greater processing power of CPU or GPU or memory capacity. A pen display utilizes the processing power of an external computer, and is categorized as a dependent or peripheral device of the external computer.
(2) Mobile Tablet Computer
On the other hand, in a mobile computer world, a mobile tablet computer including a CPU, memory, and a touch/pen sensor with a display has been widely used. A tablet computer, which may run on battery power and whose processor is controlled by its own operating system (OS), is originally designed to be used independently of other computers (“mobile mode”). A user of such tablet computer may utilize a positional input sensor, typically a touch sensor, to interact with the OS and application software to, for example, send emails or surf the web. A tablet computer's processor, in part due to its compact size, is often inadequate for carrying out computationally intensive processing such as graphics data processing.